Filter devices of this type are readily available commercially in different designs. To a large extent, these filter devices are used for filtration of working fluids, such as hydraulic fluids, fuels, lubricants, and the like. Such device in the form of a suction filter is described, for example, in brochure D7.108.2/06.07 of Hydac Filtertechnik GmbH with the product description of RKM return line suction filter, and is commercially available in different pressure stages (up to 10 bar) and for different return volumetric flows (up to 800 l/min).
Return line suction filters are used in hydraulic systems in those cases in which there are both an open hydraulic circuit (for example, working hydraulics) and a closed hydrostatic system (for example, traction drive) in the system. In this connection, return line suction filters can perform both the function of the return line filter of the open circuit and the function of the suction filter of the closed circuit (drive), provided that the return flow of the open hydraulic system is not less than the volumetric flow of the feed pump for the hydrostatic system. In fluid systems, specifically hydraulic systems, in which filter devices are used, the operating reliability of the system depends largely on the reliable operation of the filter device located in the system. In other words, failure of the filter device, beyond the failure of the pertinent system, can lead to serious damage to the system and thus can cause significant financial losses.